How to make usercontrol3 not on top of usercontrol1

though i create user control3 later than control1, i set tabindex

UserControl3 win3 = UserControl3.getInstance();
            UserControl1 win1 = UserControl1.getInstance();
            UserControl2 win2 = UserControl2.getInstance();
            win3.TabIndex = 1;
            win1.TabIndex = 2;
            win2.TabIndex = 3;

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